Various orally disintegrating tablets are currently available on the market. These tablets include a disintegrant and usually a pharmaceutically active ingredient (“active ingredient”) and disintegrate or dissolve without a chewing action in less than three minutes, usually in less than 60 seconds, upon contact with saliva, forming a suspension of small particles which is easy to swallow.
Once easily swallowed, the particles containing the active ingredient release the same most preferably into the stomach or into the upper part of the gastrointestinal tract.
This type of tablet is described, for example, in documents EP 548 356, EP 636 364, EP 1 003 484, EP 1 058 538, WO 98/46215, WO 00/06126, WO 00/27357 and WO 00/51568.
Orally disintegrating tablets are a convenient route for swallowing active agents since they do not require, but not exclude, absorbing water at the same time.
Owing to its ease of use, the orally disintegrating tablet is entirely suitable for ambulatory treatment, more particularly for certain patients and especially the elderly or young children, who have difficulties in swallowing such that they find it unpleasant, or even impossible, to ingest tablets or gel capsules, even with a simultaneous intake of liquid.
It is estimated that 50% of the population experiences such difficulties, with the possible consequence of the prescribed medicinal product not being taken and thus a major impact on the efficacy of the treatment (H. Seager, 1998, J. Pharm. Pharmacol. 50, 375-382).
In the case where the active ingredient has for instance a bitter or an unpleasant taste, the small particles may consist of coated granules containing the said active ingredient, thus preventing a bad taste from developing in the mouth. Such coating can also be provided to prevent the active ingredient from being prematurely released in the mouth or to ensure delayed release in the stomach. A typical coating for taste-masking is an aminoalkyl methacrylate copolymer sold by Röhm Pharma Polymers (Degussa) as EUDRAGIT® E 100 or EPO, namely dimethyl aminoethyl methacylate copolymer, comprising a functional group with tertiary amine.
This coating is insoluble at a pH above 5.5, thus remains intact in contact with saliva but is readily soluble in gastric juice, due to the protonation of the amine functions, thus releasing the active ingredient in an immediate manner in the stomach.
However, the Applicant has discovered that this copolymer is not suitable for making conventional coated granules for direct tableting from oxycodone in the form of a base or a pharmaceutically acceptable salt such as oxycodone hydrochloride which is prescribed to relieve pain.
It has been observed by the Applicant that the oxycodone content of such granules tends to decrease with time due to the degradation of oxycodone into oxidation by-products such as oxycodone N-oxide and oxymorphone. Without intending to be bound by any theory, it is believed that the nitrogen atom of the tertiary amines of the dimethylaminoethyl methacrylate units of Eudragit® E100 may form hydrogen bonding with the hydrogen atom of the ammonium function of oxycodone hydrochloride, which in turn could facilitate oxidation reactions. Peroxides or other contaminants, originating from other excipients or active ingredients, are also susceptible to induce oxidative degradation of oxycodone.
Now, it is preferable that the final tablets retain as much oxycodone for as long as possible under storage conditions. This is both so that the efficacy of the tablet remains high, and so that the degradents and impurities produced by the breakdown of the active ingredients remain low. Specifically, it is preferable that at least about 90% of the oxycodone, and more preferably at least about 95% of the oxycodone remain after storage for 14 days, and more preferably after 21 days at 80° C. dry heat.
Oxycodone is for instance marketed as conventional tablets alone as an hydrochloride salt under the trademark Roxicodone®, or in combination with acetaminophen, by ENDO PHARMACEUTICALS under the trademark Percocet®.
However, formulating orally disintegrating tablets including both oxycodone and acetaminophen proved to be difficult, since it has been discovered that acetaminophen can promote the degradation of an opiate such as oxycodone by direct interaction especially in moist conditions or in the presence of residual humidity.
It has also been observed that acetaminophen release was also slowed down when acetaminophen crystals were combined with oxycodone hydrochloride in taste masked granules prepared according to US 2006/0134422, further dispersed within an orally disintegrating tablet. Thus standard methods of isolating oxycodone from acetaminophen can delay the release of the two active agents and undesirably delay the onset of pain relief to the patient.
For the purposes of the present invention the expression “orally disintegrating tablets” refers to a tablet which disintegrates or dissolves in the mouth in less than 60 seconds, preferably in less than 40 seconds upon contact with saliva, forming therefore small particles which are easy to swallow.
The disintegration time here corresponds to the time between the moment when the tablet is placed on the tongue and the moment when the suspension resulting from the disintegration or dissolution of the tablet is swallowed.
Thus, there remains a need for orally disintegrating tablets in which a peroxide-sensitive active agent such as oxycodone can be included without experiencing any substantial degradation, either alone or in combination with acetaminophen.
Moreover, there remains a need for a means for orally delivering a stable form of oxycodone to the gastrointestinal tract while avoiding premature release thereof in the mouth.
In addition, it would be desirable to provide for an orally disintegrating tablet comprising both oxycodone and acetaminophen while offering not only stable oxycodone, but also a good dissolution rate of acetaminophen, i.e. a release of 85% wt of acetaminophen from a tablet including 325 mg thereof, in less than 10 minutes at any pH ranging from pH 1.2 to pH 6.8 and at least 90% release of acetaminophen at 15 min. It would also be desirable to provide for an orally disintegrating tablet comprising both oxycodone and acetaminophen while having a Cmax of acetaminophen between 4.5 and 6.8 ng/mL for a tablet including 10 mg oxycodone and 325 mg acetaminophen and providing for a fast dissolution rate of acetaminophen at an acidic pH, such as in the stomach.
The object of this invention is thus to propose new dosage forms of oxycodone enabling to solve the above needs.